Contact lenses need to be periodically treated, for example, disinfected, cleaned soaked and the like, because of the tendency for a variety of microbes and other materials to accumulate on the lenses. An efficacious disinfecting/cleaning regimen removes these accumulations and provides a contact lens that is safe and comfortable to wear.
Rigid, gas permeable and soft materials are produced from different materials having different chemical and physical properties. Lenses made from these different materials tend to accumulate different types of deposits. Because different lenses tend to accumulate different types of deposits, it is difficult to formulate a cleaner that is effective against all of the deposits, especially those deposits that are proteinaceous or sebaceous.
Conventional contact lens cleaning solutions contain one or two general classes of cleaners. Surfactant cleaners, generally known as daily cleaners because of their recommended daily use, are effective for the removal of most carbohydrate and lipid (sebaceous) materials. Enzymatic cleaners, on the other hand, contain proteolytic enzymes and are typically recommended for weekly use to remove proteinaceous material such as lysozyme.
Rigid gas-permeable (RGP or “hard”) contact lenses and hydrogel (“soft”) contact lenses require different types of cleaners. Daily cleaners for RGP contact lenses usually contain both a surfactant and a mechanical abrasive. The user cleans the RGP lenses by rubbing the lens with the cleaning composition to remove the debris. Combinations of surface active agents and mechanical cleaners are disclosed in U.S. Pat. No. 4,394,179 to Ellis et al.
A typical method for daily cleaning contact lenses comprises the steps of:                (1) removing the contact lens from the eye;        (2) applying a cleaner to the contact lens;        (3) rubbing the contact lens with the cleaner; and        (4) rinsing the contact lens.        
Rinsing solutions are normally used to remove any cleaner left on the lens after cleaning. The rinsing solution must also be compatible with the ocular environment as some solution will remain on the lens and be transferred into the eye when the lens is inserted.
With conventional abrasive cleaners, the lens needs to be thoroughly rinsed to avoid carrying residual amounts of cleaner into the eye. Conventional abrasive cleaners need to be removed from the lens before placing the lens in the eye because conventional abrasive cleaners can cause both mechanical abrasion and chemical irritation if placed in the eye. Aqueous suspensions of polymeric beads such as those disclosed in U.S. Pat. No. 4,655,957 to Chromececk and European Patent Application No. 0 063 472 to Su have proven to be effective cleaning agents for removing deposits on contact lenses. In particular, U.S. Pat. No. 4,655,957 discloses an aqueous suspension having 0.001 to 25 weight percent of a particulate hydrophilic polymer in a buffered, isotonic solution containing one or more surfactants and optional preserving and sequestering agents.
European Patent Application No. 0 063 472 discloses a cleaner which comprises a suspension containing a particulate organic polymer or polysiloxane of a hydrophobic, thermoplastic nature.
European Patent Application No. 0 063 472 and U.S. Pat. Nos. 4,613,379; 4,670,060; 4,792,414; and 5,037,484 (all to Su et al.) disclose a composition and method for cleaning contact lenses with a particulate organic polymer or polysiloxane with a carrier. The particulate polymer is selected from the group consisting of organic polymers, polysiloxane polymers and mixtures thereof. The polysiloxane is of a hydrophobic, thermoplastic nature. The resulting composition is compatible with ocular tissue and has a viscosity sufficient to keep the particulate polymer suspended within the carrier. The particulate polymers should have a degree of hardness and shape so as to be effective as a cleaning agent but yet not have the ability to scratch the lens.
Abrasive cleaners need to remove deposits from contact lenses without scratching the surface of the lenses. The abrasive beads used in the abrasive cleaner may be hydrophobic or hydrophilic. Conventional hydrophobic beads tend to have higher surface hardness and bulk rigidity than hydrophilic beads. Conventional hydrophilic beads, while softer and less likely to scratch the surface of the contact lens, tend to agglomerate and sink out of suspension. Thus they tend to fall on the bottom and eventually cake together, requiring the consumer to vigorously shake the bottle to re-suspend the beads